From nobody Sun Sep 14 03:49:36 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E1BC7C05027 for ; Thu, 26 Jan 2023 16:16:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231634AbjAZQQS (ORCPT ); Thu, 26 Jan 2023 11:16:18 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53432 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229730AbjAZQQQ (ORCPT ); Thu, 26 Jan 2023 11:16:16 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 11EEC1BDC for ; Thu, 26 Jan 2023 08:16:15 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 9FDE1618BB for ; Thu, 26 Jan 2023 16:16:14 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E0601C433EF; Thu, 26 Jan 2023 16:16:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1674749774; bh=kpO4X4ciaqU1KybKz9EuWl1FehzDKISrOewl41Tfjt8=; h=From:To:Cc:Subject:Date:From; b=Fg25g3sqdtvEn2lld+9h1q7vBOPNK3Mvam7nrVA8Xtph/MQWRPfXM4bSUligYxw2E 3D/9zGFB3uONVr+7WEHMcccAq6muVuCtIarbMVFett0G4ME/U6APha1oWyarnFVpUU mTSucSO8aeLCdWPZDHQOaego2FTHkr9QX1aQlzV0sWV9wpgFuBP5seRFx4Mz4FyohC uQbIcYGfCAL5kk55ZLTpPrQMPFNH9sCElbizaRwEkyjp5hQTBV8h61zsE9kfgP9GcQ aD6DOkUnMdPCFFh1i0XvADZmTOq4hdqLpUqeAH0h/T8tJjfrMcli2OH6o7zWkS7/Iz 1IUWkTotoUPvQ== From: guoren@kernel.org To: guoren@kernel.org, palmer@dabbelt.com, paul.walmsley@sifive.com, mhiramat@kernel.org, conor.dooley@microchip.com, penberg@kernel.org, mark.rutland@arm.com Cc: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, Guo Ren Subject: [PATCH] riscv: kprobe: Optimize kprobe with accurate atomicity Date: Thu, 26 Jan 2023 11:15:59 -0500 Message-Id: <20230126161559.1467374-1-guoren@kernel.org> X-Mailer: git-send-email 2.36.1 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: Guo Ren The previous implementation was based on the stop_matchine mechanism, which reduced the speed of arm/disarm_kprobe. Using minimum ebreak instruction would get accurate atomicity. This patch removes the patch_text of riscv, which is based on stop_machine. Then riscv only reserved patch_text_nosync, and developers need to be more careful in dealing with patch_text atomicity. When CONFIG_RISCV_ISA_C=3Dn, the ebreak could replace the whole instruction. When CONFIG_RISCV_ISA_C=3Dy, the patch uses 16-bit length c.ebreak instruction, which may occupy the first part of the 32-bit instruction and leave half the rest of the broken instruction. Because ebreak could detour the flow to skip it, leaving it in the kernel text memory is okay. Signed-off-by: Guo Ren Signed-off-by: Guo Ren --- arch/riscv/include/asm/patch.h | 1 - arch/riscv/kernel/patch.c | 33 ------------------------------ arch/riscv/kernel/probes/kprobes.c | 29 ++++++++++++++++++-------- 3 files changed, 21 insertions(+), 42 deletions(-) diff --git a/arch/riscv/include/asm/patch.h b/arch/riscv/include/asm/patch.h index 9a7d7346001e..2500782e6f5b 100644 --- a/arch/riscv/include/asm/patch.h +++ b/arch/riscv/include/asm/patch.h @@ -7,6 +7,5 @@ #define _ASM_RISCV_PATCH_H =20 int patch_text_nosync(void *addr, const void *insns, size_t len); -int patch_text(void *addr, u32 insn); =20 #endif /* _ASM_RISCV_PATCH_H */ diff --git a/arch/riscv/kernel/patch.c b/arch/riscv/kernel/patch.c index 765004b60513..8bd51ed8b806 100644 --- a/arch/riscv/kernel/patch.c +++ b/arch/riscv/kernel/patch.c @@ -98,36 +98,3 @@ int patch_text_nosync(void *addr, const void *insns, siz= e_t len) return ret; } NOKPROBE_SYMBOL(patch_text_nosync); - -static int patch_text_cb(void *data) -{ - struct patch_insn *patch =3D data; - int ret =3D 0; - - if (atomic_inc_return(&patch->cpu_count) =3D=3D num_online_cpus()) { - ret =3D - patch_text_nosync(patch->addr, &patch->insn, - GET_INSN_LENGTH(patch->insn)); - atomic_inc(&patch->cpu_count); - } else { - while (atomic_read(&patch->cpu_count) <=3D num_online_cpus()) - cpu_relax(); - smp_mb(); - } - - return ret; -} -NOKPROBE_SYMBOL(patch_text_cb); - -int patch_text(void *addr, u32 insn) -{ - struct patch_insn patch =3D { - .addr =3D addr, - .insn =3D insn, - .cpu_count =3D ATOMIC_INIT(0), - }; - - return stop_machine_cpuslocked(patch_text_cb, - &patch, cpu_online_mask); -} -NOKPROBE_SYMBOL(patch_text); diff --git a/arch/riscv/kernel/probes/kprobes.c b/arch/riscv/kernel/probes/= kprobes.c index 475989f06d6d..27f8960c321c 100644 --- a/arch/riscv/kernel/probes/kprobes.c +++ b/arch/riscv/kernel/probes/kprobes.c @@ -24,12 +24,18 @@ post_kprobe_handler(struct kprobe *, struct kprobe_ctlb= lk *, struct pt_regs *); static void __kprobes arch_prepare_ss_slot(struct kprobe *p) { unsigned long offset =3D GET_INSN_LENGTH(p->opcode); +#ifdef CONFIG_RISCV_ISA_C + u32 opcode =3D __BUG_INSN_16; +#else + u32 opcode =3D __BUG_INSN_32; +#endif =20 p->ainsn.api.restore =3D (unsigned long)p->addr + offset; =20 - patch_text(p->ainsn.api.insn, p->opcode); - patch_text((void *)((unsigned long)(p->ainsn.api.insn) + offset), - __BUG_INSN_32); + patch_text_nosync(p->ainsn.api.insn, &p->opcode, offset); + patch_text_nosync((void *)((unsigned long)(p->ainsn.api.insn) + offset), + &opcode, GET_INSN_LENGTH(opcode)); + } =20 static void __kprobes arch_prepare_simulate(struct kprobe *p) @@ -114,16 +120,23 @@ void *alloc_insn_page(void) /* install breakpoint in text */ void __kprobes arch_arm_kprobe(struct kprobe *p) { - if ((p->opcode & __INSN_LENGTH_MASK) =3D=3D __INSN_LENGTH_32) - patch_text(p->addr, __BUG_INSN_32); - else - patch_text(p->addr, __BUG_INSN_16); +#ifdef CONFIG_RISCV_ISA_C + u32 opcode =3D __BUG_INSN_16; +#else + u32 opcode =3D __BUG_INSN_32; +#endif + patch_text_nosync(p->addr, &opcode, GET_INSN_LENGTH(opcode)); } =20 /* remove breakpoint from text */ void __kprobes arch_disarm_kprobe(struct kprobe *p) { - patch_text(p->addr, p->opcode); +#ifdef CONFIG_RISCV_ISA_C + u32 opcode =3D __BUG_INSN_16; +#else + u32 opcode =3D __BUG_INSN_32; +#endif + patch_text_nosync(p->addr, &p->opcode, GET_INSN_LENGTH(opcode)); } =20 void __kprobes arch_remove_kprobe(struct kprobe *p) --=20 2.36.1